As generally indicated above, the current invention is addressed to a method and apparatus for synchronizing waveform data and an associated video. Although the method and apparatus are generally directed to the evaluation of insect behavior, the technology has multiple other applications associated with the evaluation of other processes and/or organisms, including human subjects. For example, the current invention could be used to synchronize a video of an individual taking a polygraph examination with the actual polygraph readout. The technology described in the current invention may also be used in conjunction with other biological/biomedical time-based evaluations such as electrocardiograms (EKGs) and other medical monitoring technologies.
The current invention was designed to monitor the feeding process of the glassy-winged sharpshooter (Homalodisca vitripennis). The insect spreads the bacterium associated with Pierce's disease (Xylella fastidiosa), which is responsible for millions of dollars in damage to California's grape vineyards as well as other commercial crops (on Sep. 26, 2008, photos of the glassy-winged sharpshooter were available at: http://danr.ucop.edu/news/MediaKit/photos/default.shtml).
Sharpshooters acquire the Xylella fastidiosa bacterium from infected plants and transmit it to healthy plants. After adult sharpshooters acquire the bacteria, it remains in the insect's mouthparts throughout the insect's life. Researchers (including the inventors) are attempting to combat Pierce's disease by better understanding how glassy-winged sharpshooters carry and spread the disease.
One means of studying the transmission of the disease is through an understanding of the way the insects feed. Electrical penetration graph (EPG) technology provides information regarding the way that the insect draws its fluid food from plants. The EPG process is initiated by attaching a gold wire to the body of a sharpshooter and placing the sharpshooter in a feeding position on the leaf of a host plant. A plant electrode is then placed in the soil adjacent to the plant or attached directly to a part of the plant. A lead wire from the plant electrode and the gold wire attached to the insect are then connected to a monitoring system.
When the stylets (the probing and penetrating mouth parts of the insect) connect with the host plant, an electrical circuit is completed. As the insect's stylets probe the host plant, the voltage in the circuit fluctuates. Researchers have been able to correlate the voltage fluctuations with certain feeding activities to better understand the biological mechanisms that facilitate the spread of the Xylella fastidiosa bacteria.
An analog-to-digital converter in the system controller converts the analog EPG voltage waveforms to a digital signal at a selectable sampling rate generally set at 100 samples per second. The digitized EPG voltage waveforms are displayed on a time-based chart that is similar in many ways to a human EKG chart. Concurrent with the EPG process, researchers also make a video recording of the insect as it feeds on the host plant. However, the prior art includes no means of precisely synchronizing the video recording of the insect with the concurrent EPG reading.
At least one researcher has attempted to synchronize the insect video with the EPG readout by creating a “master” video that includes both the EPG readout and the insect video within the same camera frame. Specifically, the researcher created a video that (within the same camera frame) included a video of the feeding insect concurrent with a computer monitor displaying the EPG readout that was generated as the insect was feeding.
However, this process was generally unsatisfactory because (among other things), the master video was essentially a video of a video and a computer monitor. Consequently the resolution of the master video was less than desired. For the information to be useful, an operator should be able to read the fine gradations on the EPG printout and the synchronization of the video and EPG data must be more precise than this method afforded. As indicated above, the EPG waveform signal is generally digitized at 100 samples per second, while standard video is displayed at 30 frames per second.
The need exists for a synchronizing system which provides a means of establishing a precisely synchronous playback of the video of the feeding insect with time-based waveform data produced by the EPG instrument. The current invention provides a reliable means of ensuring that the video and the waveform data can be accurately synchronized.